Recent research in this laboratory has described to anomalous nuclear estrogen binding macromolecules in human breast cancer. These two entities are 1) the uncharged (unoccupied) nuclear estrogen receptor and 2) the nuclear Type II estrogen binding sites. Information about these two anomalous nuclear receptors may provide insight into the regulatory processes of human breast cancer. More immediately, information about these two anomalous nuclear receptors will be required to develop specific and accurate assays of charged (occupied) nuclear estrogen receptors. Such assays for charged nuclear estrogen receptors, alone or in concert with present techniques, promise significant improvements in the degree of accuracy of the predictions of response to endocrine manipulation in patients with metastatic breast cancer. Human breast cancer tissue will be pooled (according to rigid histologic and biochemical criteria) and used as the experimental tissue for this study. The affinity of uncharged nuclear estrogen receptor (ER) for the chromatin will be contrasted with the affinity of the charged nuclear ER. Using a competitive displacement assay, we will determine if charged and uncharged nuclear ERs bind to the same nuclear acceptor site. The nuclear Type II estrogen binding sites will be biochemically characterized. The estrogen binding characteristics will also be determined. Using anti-ER antiserum (provided by Dr. E. V. Jensen), the cross-reactivity of the nuclear Type II EBS for the anti-ER antiserum will be determined. The information obtained will be used to design an accurate and valid assay for the charged nuclear ER.